Comparison among different geoid solutions for the Egyptian south-western desert using FFT technique

Different geoid solutions for the Egyptian south-western desert are carried out in this investigation. The available data for this paper: are 2682 measured gravity values and a set of fine 30″ x 30″ and coarse 3′ x 3′ Digital Height Models for the area under investigation. The EGM96 geopotential earth model has been used for removing the effect of the reference filed from the gravity data. The geoid is computed using various gravity reduction techniques. They are: the free-air, the Airy-Heiskanen isostatic, the Pratt-Hayford isostatic, the Vening Meinesz isostatic, the Helmert condensation and the Rudzki inversion reduction techniques. The reduced gravity anomalies are gridded on a 3′ x 3′ geographical grid using the least-squares interpolation technique with local covariance functions. These gridded reduced anomalies are used to compute the different geoid solutions in the frequency domain using the spherical 2D FFT technique. The relative difference between the different geoid solutions has an internal accuracy of about 2.5 cm.